This invention relates to the art of distance measuring apparatus, and more particularly to a new and improved measuring device in the form of a tape rule providing digital display of measured distance readings.
The present invention involves the application of miniaturized digital electronics technology to a conventional coilable tape rule to provide a visual digital display of length readings. Advantages of such a digital tape rule would include the storage of previous readings while a present measurement is being made, sequential display of individual stored readings upon demand, the indication of equality between a displayed reading and a measurement made, the ability to add accumulation and calculation means to the device for processing stored readings, the selection of various modes of measurement such as inside or outside relative to the device housing, and the conversion of length readings to various measuring systems, such as English or Metric, prior to display.
In the design of such a digital tape rule, a number of considerations are involved. For example, the electronics should track the position of the measuring element or blade both during extension and return. In other words, the system should have bi-directional capability to indicate net distance traversed. The design should be compatible with a conventionally-configured and graduated tape measuring blade so that the tape rule is both human readable and machine readable. The system should read and display the measured distance traversed by the blade with a high degree of accuracy, with the capability of indicating any errors, and with the ability to accomodate a wide range in blade speed, including zero velocity.